Pipe Conditioning Tool

ABSTRACT

A pipe conditioning tool comprising a drive unit to move the tool along a pipe and a work head rotatable about an axis of the pipe to condition a surface of the pipe, the drive unit includes a frame extending to opposite sides of the pipe, the frame having legs extending radially beyond the work head to provide support for the tool upon removal from said pipe.

FIELD OF THE INVENTION

This invention relates, generally, to pipeline surface preparationsystems. More particularly, it relates to machines that travel along thelength of a pipeline to perform conditioning operations such as coatingremoval, surface cleaning and recoating.

DESCRIPTION OF THE PRIOR ART

Pipelines used to carry materials such as oil, gas and water are formedfrom sections of pipes welded end to end. During manufacture, thesections of pipe are usually coated on their exterior surface to inhibitcorrosion of the pipe material. The ends of the pipe are not coatedprior to welding so that after welding, it is necessary to coat thegirth weld to provide an integrity of coating. As part of themaintenance protocol, it is necessary, periodically, to remove thecoating from the entire pipe, prepare the surface for recoating, andapply a coating to the surface.

Pipelines are typically buried so removal of the coating requires thepipeline to be excavated and lifted to allow access to the pipe. Manualremoval of the coating is laborious and potentially dangerous due tomaterials used and the potential to damage the surface of the pipe.Machines have been proposed that are intended to be supported on andmove along the pipe to remove the coating. However, earlier devices areso heavy that a crane is needed to lower them into position atop a pipe.The weight of such devices causes the pipe to sag and thus limits thelength of pipeline that can be excavated at any onetime. When a cranedrops a heavy pipeline surface preparation systems onto a pipeline,there is a risk of damage and ultimately catastrophic explosions mayoccur.

U.S. Pat. No. 5,238,331 to Chapman describes a pipeline surfacepreparation system that is sufficiently light-in-weight to enable a teamof two workers to place it into position around a pipeline in theabsence of lifting machinery. A frame surrounds the pipeline andsupports wheels that engage the surface of the pipeline and enable thepipeline surface preparation system to travel along the extent thereof.The Chapman apparatus employs water jets to strip coating from apipeline. Water nozzles are circumferentially spaced about the perimeterof the pipeline and limit switches are employed to cause the frame thatcarries the nozzles to reciprocate along a circumferential path oftravel so that hoses connected to the apparatus are not wrapped aroundthe pipeline as the apparatus advances along the length thereof.

U.S. Pat. No. 6,832,406 to Boos describes a machine that is used toremove ah old coating from a pipe. The pipe is enclosed within a shroud.Debris removed from the pipe surface is removed from the shroud by avacuum line so it may be filtered and disposed of effectively. Themachine shown in U.S. Pat. No. 6,832,406 has been used commercially withsuccess. The arrangement of water nozzles and controls avoids thepotential damage to the pipe surface if the machine encountersunforeseen obstacles and the overall design allows the machine to bepositioned on the pipeline by workers and operate within the confines ofthe excavation.

Similar machines may be used to blast the pipe surface after the coatingis removed and then to apply a new coating. As such a train of machinesare located on the exposed length of pipe. Because it is only practicalto expose a limited length of pipe at a time, it is preferable that themachines are easily removed and can be set aside while additionalexcavation is undertaken.

OBJECT OF THE INVENTION

It is therefore an object of the present invention to obviate ormitigate the above disadvantages.

SUMMARY OF THE INVENTION

According to one aspect of the present invention there is provided apipe conditioning tool comprising a support frame, a guide member onsaid support frame to permit movement of said frame along a surface of apipe, a work head carried by said frame and operable to perform work onsaid surface, said support frame having a pair of legs at spacedlocations to pass to opposite sides of said pipe, whereby said legsprovide a stable support for said tool when said tool is removed fromsaid pipe.

Preferably, the tool includes a drive on the frame to engage the surfaceand move the frame along the pipe.

Preferably also, the tool includes a pair of arms pivotally secured tothe frame and each carrying a guide member. The arms are swingable froman open position in which the arms are spaced apart to permit a pipe topass between and an engaged position in which said guide members engagethe surface and inhibit removal of the frame from the pipe.

As a further preference, the work head oscillates relative to the frameabout said pipe.

Embodiments of the invention will now be described by way of exampleonly with reference to the accompanying drawings in which

FIG. 1 is a side perspective view of one embodiment of a pipeconditioning tool;

FIG. 2 is a front perspective view of the tool of FIG. 1 located on apipe;

FIG. 3 is a front elevation of the tool of FIG. 1;

FIG. 4 is a perspective view from the opposite side of FIG. 1 withportions of the tool removed for clarity;

FIG. 5 is an enlarged view of the machine of FIG. 4 from an oppositeside;

FIG. 6 is a view of a part of the tool shown in FIG. 5 with componentsseparated for clarity;

FIG. 7 is an end view of the machine of FIG. 4 with components moved toone extreme position;

FIG. 8 is a plan view of the tool of FIG. 1;

FIG. 9 is a perspective view, similar to FIG. 1, with additionalcomponents added;

FIG. 10 is an end elevation of FIG. 9;

FIG. 11 is a detailed view of a part of the embodiment showing part ofthe control mechanism;

FIG. 12 is a schematic presentation of placement of control componentsshown in FIG. 11;

FIG. 13 is a perspective view of an alternative embodiment of pipeconditioning tool;

FIG. 14 is a perspective view of a further embodiment of pipeconditioning tool;

FIG. 15 is an end view of the machine of FIG. 14;

FIG. 16 is a section on the line A-A of FIG. 15;

FIG. 17 is a perspective view of the components shown in FIG. 16;

FIG. 18 is a perspective view of a still further embodiment;

FIG. 19 is an end view of FIG. 18;

FIG. 20 is an enlarged perspective view of a portion of FIG. 18;

FIG. 21 is a plan perspective view of FIG. 20;

FIG. 22 is a side perspective view of the embodiment of FIG. 18;

FIG. 23 is an enlarged end view of a portion of FIG. 19;

FIG. 24 is a view similar to FIG. 23 of a further portion of the machineof FIG. 19; and

FIG. 25 is a side view of the portion shown in FIG. 24.

Initially, an embodiment will be described in the context of a machineto condition and/or coat a pipe after the previous coating has beenremoved, but, as will be appreciated from the subsequent embodiments,certain features may be utilized for machines to remove coating from apipe and to apply a coating to a girth weld.

Referring to the drawings, a pipe conditioning tool 10 used to prepare asurface of a pipe has a support frame 12 that carries a work head 14 anda shroud 16. As can best be seen from FIG. 4, the tool 10 is arranged tostraddle a pipe P so as to be moveable along the longitudinal axis x-xof the pipe P and perform work on the exterior surface of the pipe P tocondition the surface. The pipe P may be an exposed length of anexisting pipe, or may be a new pipe being prepared for installation.Such conditioning can include removal of existing coatings, surfacepreparation and recoating of the exterior surface, although in theembodiment shown in FIGS. 1-12, the machine is used for applying acoating to a pipe.

The support frame 12 includes a pair of yokes 18, 20 spaced apart alongthe longitudinal axis of the pipe P and connected by a saddle 22. Eachof the yokes 18, 20 has a pair of laterally spaced legs 24, 26 that areinterconnected by a plate 28 that forms the bight of the yoke 16, 18.The edge 30 of the plate 28 facing the pipe is arcuate so as togenerally conform to the outer surface of the pipe P. Lower ends of thelegs 24, 26 on each side of the pipe P extend radially beyond the workhead 14 and shroud 16 and are connected by a longitudinal frame member25 to provide a foot for an additional bearing surface for the legs 24,26.

The plate 28, adjacent work head 14, carries a drive gear 32 and a setof guide rollers 34 that are arranged around the circumference of acircle to support a drive ring 36. The drive ring 36 has an annularouter band 38 with a inwardly directed flange 40. Teeth 42 are formed onthe radially inner edge of the flange 40. The drive ring 36 is formedfrom upper and lower part circular sectors 36 a 36 b which are pivotallyconnected at a hinge point 44. A latch 46 secures the upper and lowersectors 36 a, 36 b, to one another at laterally spaced locations to forma continuous ring 36.

The drive gear 32 and guide rollers 34 each include a hub 48 with a pairof rims 50 on opposite sides of the hub 48. The hub 48 and rims 50support the flange 40 of the ring 36 which is received between the rims50 and thus guide it for rotation about the axis of the pipe in a planeorthogonal to the axis of the pipe.

The hub 48 of the driven gear 32 is formed as a sprocket with externalteeth 52 that are complementary to and engage the teeth 42 of the ring36. Rotation of the driven gear 32 thus causes rotation of the ring 36with the guide rollers 34 maintaining the ring in the required location.

The ring 36 carries one or more work heads 14 most clearly shown inFIGS. 4 to 6. In the embodiment shown, the work head 14 is a spray headintended to deposit a coating on to the outer surface of the pipe P. Itcould however be a sand blasting head, as shown in FIG. 13, used toremove corrosion or other contaminants from the surface prior tocoating, or could be a water jet intended to break and remove a fibrouscoating applied to the pipe P.

In the embodiment of FIGS. 1-12, a single work head 14 is provided and,as described more fully below, provision is made for rotating the workhead 14 through more than 360°. In the embodiment of FIG. 13, threenozzles 14 are disposed at 120° intervals around the ring 36, allowingthe work heads to be reversed after a smaller segment.

The work head 14 includes an axial shaft 54 that carries a spray nozzle56 at one end. The nozzle 56 is of known construction and will not bedescribed in greater detail at this time. As shown in FIG. 6, theopposite end of shaft 54 to the nozzle 56 is secured by a splinedcoupling 58 to a radially projecting mounting tab 60 formed on the outeredge of the band 38. The shaft 54 is secured to the spline 58 by adetent (not shown) to hold the shaft in a fixed orientation relative tothe ring 36.

The head 14 is connected to a material supply through a hose 64. Thesupply may be a source of high-pressure water, coating material orabrasive grit depending upon the particular conditioning operation to beperformed.

Referring again to FIG. 1, the shroud assembly 16 is carried on the ring36 and includes axial brackets 72 secured to the flange 40 of the ring36. Arcuate panels 74 are connected to the brackets to extend about thepipe P. The panels 74 are assembled in two segments with a hinge 76 andlatch 78 located at similar locations as the hinge 44 and latch 46connecting the sectors 36 a, 36 b of ring gear 36. In this way, theshroud and ring may be opened to allow the tool to be placed over thepipe P.

A horseshoe shaped fixed cover 80 is secured within the shroud 16 so asto cover the upper portion of the ring 36. The work head 14 projectsaxially beyond the shroud 16, although the shroud may be adapted toallow the work head 14 to be located within the shroud and contain theconditioning material if desired.

The driven roller 32 is mounted on a bearing 82 on the yoke 18 andconnected to a drive shaft 84 FIG. 8. The drive shaft 84 extends throughthe yoke 18 toward the yoke 20 and is coupled to a transmission 86 thatis mounted on a shelf 88 secured to the yoke 20. An electric motor 90 ismounted on the transmission 86.

A pair of stretcher plates 92 extend between the yokes 18, 20 andsupport a platform 94. A drive motor 96 is mounted on the platform 94and acts through a transmission 98 to control rotation of a drive wheel100. The drive wheel 100 is rotatably mounted on bearings 102 betweenthe stretcher plates 92 for rotation about an axis transverse to thelongitudinal axis of the pipe P. The drive wheel 100 has a concave outersurface to conform generally to the outer surface of the pipe. The outersurface of the drive wheel 100 is typically a rubber or similar compoundto provide grip to the surface sufficient to be able to move the tool 10along the axis of the pipe when required.

A similar roller 103 is provided to support the rear of the drive unitand typically is not driven, although the transmission may drive it aswell if preferred.

Control of the drive motor 96 and motor 90 is provided through a logiccontrol panel 104 that is mounted between the yokes 18, 20 on the saddle22. The control panel 104 incorporates logic control devices of aconventional nature to control the operation of the motors 90, 96 in amanner to be described below.

A pair of swing frames 106, 108 are pivotally secured to lugs 110. Theswing frames 106, 108 each include a pair of arms 112 connected to across member 114. One end of the arms 112 is pivotally connected to thelugs 110 for movement about an axis generally parallel to thelongitudinal axis of the pipe.

A pair of guide wheels 116, 118 are connected to respective ones of thecross members 114 at longitudinally spaced locations. The guide wheels116, 118 are oriented to roll along the surface of the pipe as the toolis moved along the longitudinal axis of the pipe.

Fixed guide wheels 120 are also secured to the saddle 22 adjacent to theyoke 20 to bear against the surface of the pipe P. The fixed guidewheels 120 support the trailing edge of the tool 10 whilst maintainingsufficient load on the drive wheels 100 to allow the wheel 100 to gripthe surface of the pipe P. A flexible strap 122 extends between theswing frames 106, 108 and is used to hold the swing frames in a positionin which the guide wheels 116, 118 engage with the underside of the pipeP. The strap is adjusted by a ratchet and pawl device 123 so it may betensioned to hold the tool in place, and released to allow removal ofthe tool.

The forward yoke 18 also carries a set of fixed guide wheels indicatedat 124 and 126. The guide wheels 124 engage the rear face of the ring 36to resist longitudinal forces, and the wheel 126 is located on theradially outer face of the ring 136 to locate the ring radially.

Limit switches 128 130 are secured to the yoke 18 and the ring 36 so asto be responsive to movement of the ring to a predetermined positionrelative to the frame 12. Limit switches 128, 130 may be mechanical,optical or, preferably proximity devices that provide control signals tothe control panel 104. In some embodiments, as described below, only asingle limit switch is required.

In operation, the tool is initially positioned to one side of the pipe Pwith the legs 24, 26 supporting the work head 14 in a stable, elevatedposition above the immediate surrounding. The tool 10 may then be liftedabove the pipe P and the strap 122 released to that the swing frames 106108 hang generally vertically along side the legs 24 26. In thisposition, the lower segment of the ring 36 and shroud 16 are unlatchedand pivoted about the hinges 44 76 to provide an inverted U-shapedconfiguration for the tool 10.

With the tool 10 elevated, it may be positioned over the pipe P andlowered until the drive wheels 100 and the fixed guide wheels 120 engagethe upper surface of the pipe P. In this position, the tool is once morestably supported on the pipe in the desired axial position. The tool 10may then be secured by swinging the swing frames 106, 108 about the lugs110 until the guide wheels 116, 118 engage the pipe surface. The strap122 is secured and tensioned to hold the wheels firmly against thesurface of the pipe. In this position, the drive wheel 100, idler 103and fixed guide wheels 120 maintain the yokes 16, 18 spaced from thesurface of the pipe but inhibit pitching motion of the frame 12.Vertical displacement of the frame 12 in inhibited by the swing frames106 108.

The lower segment of the ring 36 and shroud 16 may then be closed aroundthe under side of the pipe and latched through latches 46, 78respectively. The hose 64 is connected to a supply of conditioningmaterial and a control panel 104 connected to a supply of electricity.

Initially, the motor 92 is operated to rotate the shaft 84 and cause thering 36 to rotate about the axis of the pipe P. The guide rollers 34maintain the circular disposition of the ring 36 and as the ring 36rotates, the work head 14 traverses a sector of the outer surface of thepipe P. After predetermined rotation, the limit switch 128 indicates thefirst extreme position of the ring relative to the frame 12. A controlsignal from the limit switch is sent to the panel 104 which causes themotor 90 to reverse and rotate the shaft 84 in the opposite direction.The ring 36 is similarly rotated in the opposite direction until, aftera predetermined rotation typically in the order of 180 degrees with asingle work head, the rotation is again reversed by the limit switch130. The work head 14 oscillates about the longitudinal axis of the pipeP so that the entire surface of the pipe is traversed.

The control panel 104 also controls the rotational speed of the drivemotor 96 which acts through the transmission 98 on the drive wheel. Thedrive wheel 100 advances the frame 12 along the pipe P causing a newarea of the pipe surface to be traversed at each oscillation of the workhead 14. The speed of advance will of course be determined by the workto be performed and the advance may be interrupted at any time shouldfurther surface conditioning be required on the pipe.

During oscillation of the work head 14, the hoses 64 are supported bythe shroud so that they may be supplied with the conditioning materialfrom a source along side the pipe.

Once the surface has been treated, the tool 10 can be removed byreleasing the strap 122 and opening the shroud 16 and ring 36. The tool10 may then be lifted, the shroud closed and the tool 10 deposited onthe ground in a stable position supported by the legs 24, 26.

As noted above, the number of work heads 14 that are utilized willdepend upon the particular circumstances and material being used.

When a single coating head 14 is utilized, the operation of theproximity switches is arranged such that a full circumference of thepipe may be traversed with the single head rather than with multipleheads as explained in greater detail below with reference to FIGS. 9through 12. This requires the movement of the hose 64 to be controlledto inhibit engagement with the shroud 16.

Referring therefore to FIG. 9, the hoses 64 are entrained within a chain111 made up of links connected in seriatim so as to be flexible in aradial plane but relatively rigid in an orthogonal plane. The chain 111is secured to a mounting post 113 and depends from the post in anelongate loop to supply fluid to a manifold 115 associated with the tool14. The post 113 may be resiliently mounted to reduce loads imposed bythe chain 111.

A pair of flexible bumpers 116 are secured to the outer surface of theshroud in alignment with the chain 111. The bumpers 116 have a convexsurface protruding outwardly from the surface of the shroud 16 and holdthe chain 111 away from the shroud. The bumpers 116 may be made fromflexible plastic or rubber-like compound with a degree of resilience.

As can be seen in FIG. 10, the pair of the bumpers 116 is disposed onopposite sides of the mast 113 with the ring 36 in the midpoint oftravel.

As the tool 14 rotates, the chain 11 Vis pulled over the bumper 116 butheld away from the side of the shrouds. The bumpers 116 increase theeffective diameter of the shroud and thus create a longer run for thechain 111. Upon reaching the limit of rotation, the chain 111 is wrappedaround a portion of the shroud 16 and over the bumper 116. Reversal ofthe tool 14 allows the chain 111 to unwind and be held away from theside of the shroud until the opposite facing bumper moves past the mast113 and again lifts the chain away from the surface of the shroud.

The movement of the chain 111 is thus controlled and its vertical limitreduced to avoid contact with the surrounding environment.

The control of the rotation of the ring 36 and the shroud 16 isperformed by a single proximity switch cooperating with a reversibleoffset actuator. As can be seen from FIG. 11, a bracket 130 is securedto the band of the ring 36 and a pendulum 132 pivotally mounted to theband. A bolt 134 projects from the pendulum 132 and engages an edge ofthe bracket 130 to limit movement toward the ring 36.

FIG. 12 shows schematically the arrangement of a proximity switch 140which is connected to the control panel 104. As the ring 36 rotatesclockwise as viewed in FIGS. 11 and 12, the pendulum 132 hangsvertically. As the bracket 130 passes the lowest point of the ring 36,the pendulum 132 will pivot relative to the bracket 130 and continuedrotation causes it to fall back against the bracket until the bolt 134engages the bracket 130. The bolt 134 is trailing the pivot point of thependulum 132 to the bracket 130 in the direction of rotation so that thepivot point moves past the proximity switch prior to actuation of theswitch. It will be appreciated the pendulum 132 carries a magnet orinsert of magnetic material to generate a signal and allow selectiveoperation of the switch 140.

Actuation ofthe switch 140 causes reversal of the ring 36 so that thependulum again will hang vertically as it passes through the lower pathof the ring. Continued movement towards the upper portion of the ringcauses the bolt 134 to engage the bracket so that it is once againtrails the pivot in the direction of rotation as it moves past theproximity device 140. Reversal again occurs.

By providing for the pendulum to move between two stable positions, thearea ofthe pipe swept by the tool slightly exceeds 360° and ensures acomplete coverage of the pipe surface.

As noted above, the pipe conditioning tool may be used in a variety ofapplications including the removal of an existing coating from a pipe.An embodiment to perform such removal is shown in FIGS. 15-17 in whichlike reference numerals will be used to identify like components with aprefix 2 added for clarity.

A support frame 212 similar to that described above with respect toFIGS. 1-12, carries a work head 214 surrounded by a shroud 216. The workhead 214 may be rotated about the axis of the pipe P by a drive gear 232cooperating with a ring gear 236. It will be noted in the arrangementshown in FIG. 14 that the ring 236 has radially outwardly directed teeth242 to engage the drive gear 232 externally. It will of course beappreciated that the internally toothed gear may also be used in thisarrangement.

The ring gear 236 carries a set of high pressure nozzles (not shown)distributed at 120 degree angles around the periphery of the ring gear236 in a manner similar to that shown in FIG. 13. The nozzles aresupplied with water through hoses (not shown) to produce a high pressurejet that impacts the surface of the pipe P. The ring gear 236 isoscillated over a 120 degree arc to enable the jets to traverse thewhole surface of the pipe P and remove the coating from the pipe.

The shroud 216 is split along its equator by flanges 276 to allow theshroud 16 to completely encompass the pipe. A brush seal 300 is arrangedaround the inner periphery of the shroud 16 to maintain contact with thepipe P and inhibit egress of contaminated water.

The shroud 216 is formed with a collection chamber 302 at its lowerpoint to serve as a collection zone for material removed from the pipe.A tubular chamber 306 is formed at the apex of the collection chamber302 and has an outlet port 308 for connection to a vacuum pipe. Debrisremoved from the pipe falls into the collection chamber 302 and into thetubular chamber 306 from where it is extracted by the vacuum pipe.

A pusher assembly 310 is provided in the tubular chamber 306 andcomprises an actuator 312 driving a piston rod 314. The actuator 312 maybe a hydraulic or air actuator or maybe a recirculating ball screw-typeactuator that can extend or retract the piston rod 314 within thetubular member 306. A tapered piston 316 is carried by the piston rod312 and is a clearance fit within the tubular chamber 306.

In operation, the tool 210 is positioned on the pipe P and secured in amanner described above. The shroud 216 is secured about the pipe at theleading edge of the tool 210 and the high pressure fluid supplied to thenozzles. At the same time, the work head 214 is caused to oscillate andthe tool 210 is advanced along the pipe by the drive motors. The coatingon the pipe P is removed by the action of the high pressure jets and isextracted through outlet port 308 by the vacuum pipe. The coating of thepipe P is typically fibrous in nature and may release in large chunks orstrips. As such it may bridge the entrance to the outlet port 308causing a gradual accumulation of the coating within the collectionchamber 302. To avoid blockage or bridging of this nature, the actuator312 is operated to extend the piston rod 314 and push materialaccumulated in the tubular chamber 306 along towards the outlet port308. The action of the piston 316 within the tubular chamber 306dislodges large portions that have bridged the tubular chamber andrelease them for movement into the exhaust duct. It has been found thatthe clearance ofthe piston from the sides of the tubular duct facilitatea clearing action of the debris causing it to move into the exhaust ductand avoid the build up of the debris.

In a typical application, the diameter of the tubular chamber is 4inches and the diameter of the piston is 2.5 inches providing aclearance between the wall of the housing and the piston in the order of0.75 inches. Obviously other dimensions may be utilized.

It will also be noted that the piston has a cortical rear face tofacilitate the passage ofthe piston through the debris when beingretracted and avoid the debris from being trapped behind the piston.

A further arrangement of pipe conditioning tool is shown in theembodiment of FIGS. 18-25 in which like components will be identifiedwith like reference numerals with a prefix 4 added for clarity. Theembodiment of FIGS. 18-25 is used to apply a coating to a girth weldformed between two sections of pipe. Typically, the coating appliedduring the manufacture of the pipe terminates prior to the end of thepipe to allow the adjacent ends of pipe sections to be welded to oneanother. Subsequent to the welding, the weld is covered to provide auniform coating over the weld and adjacent areas.

The pipe conditioning tool 410 includes a support frame 412 with a pairof spaced apart yokes 418, 420. The yokes 418, 420 are formed ascircular hoops 500 that completely circumscribe the pipe. The hoops 500may be formed as a continuous member as they may be slipped on the freeend of a pipe and moved along the pipe between welds or, moreconveniently, may be formed as two part circular segments in the mannerdescribed above with respect to the upper and lower sectors of the drivering 36 and as shown by the hinge 501 in FIG. 23.

The hoops 500 are maintained in space relationship by curved stringers502 spaced apart around the circumference of the hoops 500. Thestringers 502 provide convenient carrying points for the tool 410 aswell as structural rigidity for the tool.

A pair of ring gears 436 are connected to respective ones of the hoops500 through radial struts 506. Adjustable clamps 508 are mounted onalternate ones of the struts to maintain the tool centered on the axisof the pipe. The clamps 508 may be threaded bolts or other telescopicsupports that may be engaged with the pipe and retracted when the tool410 is to be moved.

Each ofthe ring gears 436 has teeth 442 directed radially outwardly andengaged a drive by gear 432. A shaft 510 extends between the drive gears432 and is rotatably supported in bearings 512. The bearings 512 areconnected to a platform 514 that provides a body of a carriage 516. Aweb 518 projects radially inwardly from the platform 514 and carries apair of guide rollers 434 that engage the radially inner face of thering gear 436. The guide rollers 434 maintain that the drive gear 432 incontact with the teeth 442 and provide a stable location for thecarriage relative to the ring gear 436.

The shaft 510 passes through a gear box 522 mounted on the platform andtransmitting drive from a motor 524 to the shaft 510. Power for themotor 524 is provided by rechargeable battery packs 526.

A coating dispenser assembly 530 is mounted on the platform 514 adjacentto the gear box 522. The dispenser assembly 530 is designed to dispensetwo components of a two pack epoxy coating from respective cartridges532, 534. The cartridges 532, 534 are received in respective bores of ahousing 535 that contains a mixing head 536. The output ofthe mixinghead 536 is connected to a dispensing tube 538. As shown in FIGS. 21 and22, two pairs of cartridges are mounted on the platform and secured by astrap 540. Each of the cartridges is a disposable cartridge with a selfcontained piston that can be connect to the mixing head through anozzle. The diameter of the cartridges corresponds to the ratio of thecomponents to be mixed to form the coating as is conventional in theart.

To expel the coating material from the cartridges, a pusher assembly 550is provided. The pusher assembly 550 includes a cross head 552 fromwhich piston rods 554 extend into each of the cartridges. The crosshead552 is connected to an actuating rod 556 of an actuator 558. Theactuator 558 can be a linear actuator of convenient form but typically ascrew and ball actuator driven by a motor 560. The motor is reversibleto extend or retract the actuating rod 556 and thereby move the pistonrods into and out of the cartridges.

The dispensing tubes 538 terminate, in nozzles 562 positioned on thecenter line of the tool 410 and abutting the pipe surface, A filter isincorporated into the tube to facilitate mixing and, in a typicalapplication, a 0.023 inch spray orifice has been found to improve themixing of the components. The tubes 538 are oriented so as to bearagainst the surface of the pipe to deliver the material directly ontothe surface of the pipe. Alternatively an applicator head such as aelongate tube with slots or a spreader blade may also be used to ensureinitial contact ofthe coating material with the pipe surface.

A trowel 570 is supported on a trailing edge of the carriage and isspring loaded into engagement with the surface of the pipe. The trowel570 is connected to the carriage through a hinge 582 which incorporatesa torsion spring to bias a blade 584 into contact with the coating.Trailing edge 586 of the trowel includes a rectilinear notch 588 thathas a width generally conforming to the exposed portion of the pipe overthe weld. A vibrator 590 is mounted on the trowel to assist indistributing the coating material.

In use, the tool 410 is slid along the pipe and positioned over thegirth weld. The clamps 508 are adjusted to make the pipe and hoops 500concentric. Cartridges 532, 534 are attached to the carriage 516 withthe rod 556 fully retracted. The motor 524 is operated to rotate theshaft 510 and the drive gear 432 and cause the carriage 516 to movealong the ring gear 436 and around the pipe. As the carriage 516 ismoved, the motor 560 on the actuator 558 is operated and progressivelydisplaces the contents of the cartridge at a predetermined rate throughthe dispensing tubes 538. The contents are deposited onto the pipe asthe carriage 516 moves around the pipe and the trowel 570 spreads thecoating material in the gap between the coating on the pipe. Thecarriage 516 continues to rotate as the contents of the cartridge aredispensed and, upon complete dispensing of the contents may continue torotate as the material is progressively spread and distributed by thetrowel 570. Once the desired finish has been attained, the motor 524 isstopped and the tool 410 may be moved to the next girth weld. The rod556 is retracted and the new cartridges placed on the carriage 516 tosupply the mixture to the next weld. This process can be repeated alongthe length of the pipeline until the girth welds are treated.

As described above, the girth welds are coated in during the assembly ofa pipeline from individual sections, but it will also be apparent thatwith a segmented ring gear 436, selective recoating of a girth weld maybe performed on a reconditioned pipeline.

Similarly, although electric controls and power is described, it will beappreciated that similar effects may be attained with hydraulic powerunits.

1. A pipe conditioning tool comprising a drive unit to move said toolalong a pipe and a work head rotatable about an axis of said pipe tocondition a surface of said pipe, said drive unit including a frameextending to opposite sides of said pipe, said frame having legsextending radially beyond said work head to provide support for saidtool upon removal from said pipe.
 2. A pipe conditioning tool accordingto claim 1 wherein a pair of arms are pivotally connected to said frameon opposite sides of said pipe and are moveable to engage said pipe tosecure said frame to said pipe.
 3. A pipe conditioning tool according toclaim 2 wherein said frame includes a pair of yokes, each having a bightextending across said pipe and a pair of said legs extends from saidbight at a spacing to accommodate side pipe.
 4. A pipe conditioning toolaccording to claim 4 wherein said arms are pivotally connected to saidadjacent said bight.
 5. A pipe conditioning tool according to claim 4where guide wheels are mounted on said frame and said arms to supportsaid frame for movement along said pipe.
 6. A pipe conditioning toolaccording to claim 5 wherein a flexible releasable fastener extendsbetween said arms to hold said guide wheels in engagement with saidpipe.
 7. A pipe conditioning tool according to claim 1 wherein a driveroller is mounted on said frame for engagement with said pipe.
 8. A pipeconditioning tool according to claim 6 wherein a pair of rollers areprovided at spaced locations on said frame.
 9. A pipe conditioning toolcomprising a drive unit to move said tool along a pipe and a work headrotatable by said drive unit about an axis of said pipe to condition asurface of said pipe, said drive unit including a ring gear havingradially inwardly directed gear teeth and a plurality of guide rollersspaced apart about said ring gear and engaging said gear teeth, a drivegear engaging said ring gear and rotatable by a drive motor to impartrotation to said ring gear, said work head being connected to said ringgear for movement therewith.
 10. The pipe conditioning tool according toclaim 9 wherein a plurality of work heads are circumferentially spacedabout said ring gear.
 11. The pipe conditioning tool according to claim9 wherein each of said guide rollers includes a hub and a pair offlanges on opposite sides of said hub, said ring gear being receivedbetween said flanges.
 12. A pipe conditioning tool according to claim 9nwherein a pair of guide wheels engage a lateral face of said ring gearat circumferentially spaced locations to support said ring gear duringrotation.
 13. A pipe conditioning tool according to claim 9 wherein saiddrive motor is reversible to impart rotation in opposite directionsabout said pipe and cause said working head to oscillate about saidpipe.
 14. A pipe conditioning tool according to claim 9 wherein reversalof said drive motor is controlled by a limit switch operable toascertain angular disposition of said ring gear.
 15. A pipe conditioningtool according to claim 14 wherein said limit switch includes a signalgenerating member carried by said ring gear and circumferentiallydisplaceable on said ring gear between a pair of positions.
 16. A pipeconditioning tool comprising a drive unit to move said tool along apipe, a shroud encompassing said pipe, a work head located in saidshroud and rotatable about an axis of said pipe to condition a surfaceof said pipe, said shroud including a collection zone to receivematerial removed from said pipe, an outlet to remove material from saidcollection zone, and a rod moveable through said collection zone towardand away from said outlet.
 17. A pipe conditioning tool according toclaim 16 wherein said collection zone includes a tubular memberconnected to said outlet and said rod moves along said tubular member.18. A pipe conditioning tool according to claim 17 wherein said rod is aclearance fit in said tubular member.
 19. A pipe conditioning toolaccording to claim 18 wherein said rod includes an enlarged head.
 20. Apipe conditioning tool according to claim 16 wherein said rod is movedby a linear actuator through said collection zone.
 21. A pipeconditioning tool according to claim 20 wherein said shroud rotates withsaid work head.
 22. A pipe conditioning tool comprising a drive unitmountable on a pipe, a work head rotatable about said pipe to conditiona surface thereof, said work head including a material dispensingassembly to deposit a material on said pipe and an applicator to conformmaterial deposited on said pipe to a predetermined configuration.
 23. Apipe conditioning tool according to claim 21 Wherein said drive unitincludes a ring gear extending about said pipe and stationary relativethereto and a drive gear connected to said work head and engaging saidring gear to move said work head relative to said ring gear.
 24. A pipeconditioning tool according to claim 23 wherein said work head includesa platform, a motor on said platform and operatively connected to saiddrive gear.
 25. A pipe conditioning tool according to claim 24 whereinsaid material dispensing assembly includes a dispenser to dischargematerial from a supply to an outlet.
 26. A pipe conditioning toolaccording to claim 25 wherein said dispenser includes a linear actuatormoveable from a retracted to an extended position to discharge material.27. A pipe conditioning tool comprising a drive unit to mount on a pipe,a work head, and a reversible drive to rotate said work head relative tosaid drive unit about said pipe, the direction of rotation of said workunit being controlled by a limit switch responsive to the angulardisposition of said work head to said drive unit, said limit switchincluding a signal generating member rotatable with said work head andcircumferentially displaceable relative thereto between a pair ofpositions.
 28. A pipe conditioning tool according to claim 27 whereinsaid signal generating member is a bar pivotally connected to said workhead and rotatable about said pivot between said pair of positions. 29.A pipe conditioning tool according to claim 28 wherein said bar carriesa signal generator at a location remote from said pivot and said signalgenerator trails said pivot in the direction of rotation.